Cartridge case plug for semifixed gun ammunition

ABSTRACT

A cartridge case plug for semifixed gun ammunition having a skirt portion adaptable for fitting into a mouth of a cartridge case and having a tapered crown portion adjacent to said skirt portion, said plug being made of a rigid polyurethane foam having a density range of between 12 and 14.5 pounds per cubic foot after molding.

United States Patent Alvin Smith ()oletic, lnd.

Apr. 24, 1969 Aug. 10, 1971 The United States 0! America as represented by the Secretary of the Navy Inventor Appl. No. Filed Patented Assignee CARTRIDGE CASE PLUG FOR SEMIFIXED GUN AMMUNITION 2 Claims, 3 Drawing Figs.

US. (l [02/95, 102/41 Int. Cl F421 9/18, F4211 9/28 Field of Search 102/39, 43 C, 95

[56] References Cited UNITED STATES PATENTS 2,394,524 2/1946 Paschke et al. 102/95 X 2,947,254 8/1960 Weiss 102/95 X 2,959,130 11/1960 Weiss et al 102/95 3,354,571 11/1967 Parker 102/95 X OTHER REFERENCES Materials; Vol. 60, No. 5; p. 244; Mid October 1964 Primary Examiner-Robert F. Stahl Attorneys-Edgar J. Brower, H. H. Losche and Paul S.

Collignon ABSTRACT: A cartridge case plug for semifixed gun ammunition having a skirt portion adaptable for fitting into a mouth of a cartridge case and having a tapered crown portion adjacent to said skirt portion, said plug being made of a rigid polyurethane foam having a density range of between 12 and 14.5 pounds per cubic foot after molding.

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ATTORNEYS CARTRIDGE CASE PLUG FOR SEMIFIXED GUN AMMUNITION STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION Semifixed gun ammunition cartridges are widely used by the military department. The U.S. Navy, for example, uses gun ammunition cartridges for its 6-, and 8-inch guns. These semifixed gun ammunition cartridges are comprised of a cartridge case, a primer, a charge of propellant, and a plug for retaining the propellant within the cartridge case. The projectile is not attached to the cartridge case and is loaded separately into a gun chamber.

I-Icretofore, the majority of cartridge case plugs have been made of cork which is an imported material and excessively expensive. Additionally, cork is dimensionally unstable and frequently fails to maintain case closure during handling and gun loading. As these cartridge case plugs break up when a gun is fired, it is most important that the pieces be sufficiently small so as not to cause a safety hazard to personnelv By way of example, a cork plug for a 5inch/38 gun should disintegrate so that no fragment will exceed a weight of one-half ounce. Frequently, however, cork pieces are observed which exceed this weight and consequently are a hazard to shipboard personnel.

In addition to the disintegration requirement, a plug must be able to withstand and absorb extreme forces of shock when the cartridge case and accompanying projectile are rammed into a gun chamber. These plugs must perfonn a buffering action so that the cartridge cases will not be deformed, as any deformation could prevent proper chambering of the cartridge casein the gun chamber.

SUMMARY OF THE INVENTION The present invention relates to a cartridge case plug which is made from polyurethane foam which has a critical density of between 12 and 14.5 pounds per cubic foot. This density is critical in order to assure satisfactory fragmentation of the plug when the ammunition is fired, and yet be able to withstand loading and ramming into a gun chamber.

The plug is cylindrical in shape and has a skirt portion which is adaptable to be secured in a cartridge case. A forward crown portion is tapered to facilitate loading of the cartridge case into the gun chamber.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a front view showing a preferred embodiment of a cartridge case plug;

FIG. 2 is a side view of the cartridge case plug shown in FIG. I of the drawing; and

FIG. 3 is a sectional view ofa cartridge case showing a plug closing one end of the case.

DESCRIPTION OF THE PREFERRED EMBODIM ENT Referring to the drawing, there is shown a cartridge cas plug II having a skirt portion 12 which fits with a cartridge case 13 and a crown portion 14. Skirt portion 12 has a tapered section 15 which facilitates the crimping of cartridge case 13 around plug 11. Crown 14 has a tapered section 16 which te rminates with a bevel 17 to facilitate the loading of the cartridge case assembly into the chamber ofa gun.

Cartridge case plug 11 is composed of a polyester based carbon dioxide expanded type of rigid polyurethane foam with a density between l2 and 14.5 pounds per cubic foot. The

material and density is critical in order to meet the military (14.18 gm.). The material and density is also critical in order that the molded plug be capable of withstanding hoisting and ramming of the cartridge assembly into the chamber of the gun. The rammer strikes the base of the cartridge assembly and pushes it and the projectile into the gun chamber. Plug 11 must act as a buffer between the cartridge case and the projectile. The shock on the plug is greatest when seating of the cartridge in the gun chamber occurs and might be as high as 50,000 gs.

Referring now to FIG. 3 of the drawing, there is shown a cartridge case 21 having inside a propellant charge 22 and a primer 23. Cartridge case 21 is closed by a sheet 24 of nitrocellulose, spacer 25, and plug 11. By way of example, spacer 25 might be made of cardboard or chipboard. Cartridge case 21 is crimped onto tapered section 15 of skirt portion 12 thereby firmly attaching plug 11 to cartridge case 21.

In addition to the selection of the material for plug 11 being critical with respect to fragmentation and severe shock, there are other requirements that must be met. For example, the material should not be adversely affected by alcohol-ether vapor. The common propellants used in semifixed gun ammunition are processed using a mixture of alcohol and ether as process solvents. After extrusion or forming, some alcohol and ether remain as residual constituents, which generally evaporate out. Since an assembled cartridge represents a closed situation, these vapors should not have a deleterious af feet on plug 11.

A test was conducted at the Naval Ammunition Depot, Crane, Ind., to determine the affect of alcohol-ether vapors on plugs 11 which were made of polyurethane foam having a density of between 12 and 14.5 pounds per cubic foot. The test was set up by placing equal volumes of ethanol and diethyl ether in a carrier of dibutyl phthalate (inert, very low vapor pressure solvent). The solution consisted of six parts alcohol, six parts ether, and parts dibutyl phthalate. The solution was placed in a sealed container in which a plug was supported in a stand such that no contact was made with the liquid. After 37 days, the plug was removed from the sealed container and any dimensions and weight changes in the plug were considered insignificant with regard to suitability of the material.

It is a requirement that when fired as a component of a service round, plug 11 must disintegrate into small fragments. For a 5inch/38 plug, the largest fragment may not exceed onehalf ounce (14.18 gm.). Ten rounds were fired and the largest fragment from each was recovered and weighed. The largest fragments range from 0.5030 grams to 3.0900 grams. The largest fragment recovered from the 10 rounds was 3.0900 grams, which is only about 22 percent of the allowed value of 14.18 grams.

It can thus be seen that the present invention provides an improved plug for a cartridge case which is economical to make, and is strong and steady, yet will disintegrate into very small fragments upon firing the round to which the plug is attached.

Iclaim:

1. A cartridge case plug for semifixed gun ammunition comprising,

a cylindrical body having a skirt portion adaptable for fitting into a'cartridge case and having a tapered crown portion extending forward of said skirt portion, said plug being made ofa rigid polyurethane foam material having a density of between 12 and 14.5 pounds per cubic foot whereby said plug disintegrates into very small fragments of firing said ammunition.

2. A cartridge case plug for semifixed gun ammunition as set forth in claim 1 wherein said foam material is a polyester based carbon dioxide expanded type of rigid polyurethane foam having a density of between 12 and 14.5 pounds per cubic footv 

1. A cartridge case plug for semifixed gun ammunition comprising, a cylindrical body having a skirt portion adaptable for fitting into a cartridge case and having a tapered crown portion extendinG forward of said skirt portion, said plug being made of a rigid polyurethane foam material having a density of between 12 and 14.5 pounds per cubic foot whereby said plug disintegrates into very small fragments on firing said ammunition.
 2. A cartridge case plug for semifixed gun ammunition as set forth in claim 1 wherein said foam material is a polyester based carbon dioxide expanded type of rigid polyurethane foam having a density of between 12 and 14.5 pounds per cubic foot. 